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Forum » SpaceEngine » Science and Astronomy Discussions » What is Dark Matter?
What is Dark Matter?
TalismanDate: Saturday, 03.12.2011, 09:15 | Message # 1
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Well, this is a hard one. cool




 
HarbingerDawnDate: Saturday, 03.12.2011, 09:31 | Message # 2
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Hard indeed! Basically, Dark Matter is the invisible stuff that seems to make up the majority of mass* in the universe. It is thought to exist based on observations of the motions of stars in galaxies, as well as galaxies in clusters, which show that there is much more gravity than can apparently be explained by normal (baryonic) matter. So the hypothesis is that there exists great amounts on massive particles that don't interact with matter in a normal manner and that cannot be directly observed, only indirectly through its effect on normal matter (i.e. the orbits of stars in a galaxy). It seems that dark matter tends to reside mostly in halos around galaxies.

As for what exactly Dark Matter IS, no one knows (we're not even 100% certain it exists), but one leading theory is that is composed of what are called WIMPs, or Weakly-Interacting Massive Particles. These particles are only theoretical, but have been suspected for years and could possibly explain Dark Matter. More than that I can't say, particle physics is not exactly my forte wink

*Note: Mass here means mass independent of energy. The majority of the combined matter-energy content of the universe is thought to be Dark Energy... but that's another topic entirely! biggrin





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Edited by HarbingerDawn - Saturday, 03.12.2011, 09:33
 
TalismanDate: Saturday, 03.12.2011, 19:21 | Message # 3
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Quote (HarbingerDawn)
but one leading theory is that is composed of what are called WIMPs, or Weakly-Interacting Massive Particles. T


Ah yes, I've heard of this. It seems probable, and they have done tests searching for WIMPs using those sealed underwater sensors which have picked up rare bounces and small interactions of uknown particles. But what do those particles do? What are their function? Perhaps it's some for of communication by extra-terrestrials? cool





 
HarbingerDawnDate: Saturday, 03.12.2011, 19:41 | Message # 4
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Quote (Talisman)
Perhaps it's some for of communication by extra-terrestrials?


Doubtful, it wouldn't make any sense to communicate with something so amazingly hard to detect. I've never heard of direct detection of WIMPs in the same manner as neutrinos (though I'm fairly ignorant on the subject); the only observations of Dark Matter that I've heard of is the gravitational effects on matter that I mentioned above, and microlensing events (staring at a distant star beyond the galactic disk and waiting for a clump of Dark Matter to move between it and Earth, focusing the star's light like a lens).
The particles don't have to have a "function" any more than protons or positrons do. They simply exist as a natural consequence of the laws of physics. The universe is a fantastically complex thing, but although it may exist for a purpose, all evidence suggests that the specific events that occur in nature do not happen for any purpose; they are just a natural consequence of the framework of this reality. As Sax Russell from the Mars trilogy would say, "That's just the way it came out in the Big Bang." cool





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